The seriation method works because object styles change over time; they always have and always will.

A good example of a change in artifact type is the development of hand-held PDAs from those first enormous cell phones. As an example of how change through time works, consider the different music recording methods that were used in the 20th century.

Archaeologists call this kind of behavior "curation" -- people then, just like today, like to hang on to old things.

But you would never have any 78s in junkyards closed before they were invented.

Archaeologically, you would expect no 78s to be found in a junkyard that was closed before 78s were invented.

There might be a small number of them (or fragments of them) in the junkyard which stopped taking junk during the first years 78s were invented.His worrying about where a pot came from and what period it dated to and what that meant to the other objects buried with it were light-years away from the ideas represented in this photo dated to 1800, in which "Egyptian pots" was considered enough information for the thinking man.Petrie was a scientific archaeologist, probably close to our first example.It isn't possible to investigate all of a junkyard, so we'll pick a representative sample of the deposit.We take our samples back to the laboratory, and count the kinds of artifacts in them, and discover that each of the junkyards have broken pieces of musical recording methods in them--old broken records, pieces of stereo equipment, 8-track cassette tapes.The gramophone sat in your parlor and certainly couldn't be carried along with you and your earbobs. When 78 rpm records first appeared on the market, they were very rare.